This invention relates to certain additives in hydraulic fluids which provide improved stabilization of the fluids.
Hydraulic fluids are well known and useful in various mechanical apparatus such as in automotive brakes. They may be clear to amber or even light brown in color. Since hydraulic fluids are highly prone to oxidation, especially at high temperatures, it is known to add various antioxidants to the fluids. Oxidation is undesirable because it eventually reduces the molecular weight of the fluids and produces corrosive products. Buffers are added to control the effects of the corrosive, oxidation products.
Certain problems continue to exist, however. Even today, hydraulic fluids are stabilized insufficiently while stored for sale. Many of the additives currently employed are effective for only a few days, in some cases only a few hours. The lack of stabilization is evidenced by the collapse of plastic bottles used to store the fluids. Presumably, this effect is due to the partial vacuum created as oxygen in the head space of the bottles reacts with the fluids.
Therefore, since stabilization continues to be a problem in modern hydraulic fluids, it would be desirable to find a combination of additives which provide improved stabilizing effect over those used currently and which provide long-term protection on the order of months, not days or hours. Such a combination would improve the quality of hydraulic fluids as well as the commercial appeal of the hydraulic fluids due to the plastic storage bottles retaining their shape rather than collapsing while in storage.
A solution to this problem is one object of the present invention.